A drive-train of an agricultural or municipal vehicle such as a tractor with a step-up gear unit is known from DE 10 2012 216 046 A1. On the drive input side, the step-up gear unit is connected to a drive engine such as an internal combustion engine, and is designed with secondarily coupled power splitting with a hydrostatic branch and a mechanical branch, such that the two branches can be summed by a summing gear system. In addition at least two transmission ratio ranges in the forward and reverse directions can be obtained, wherein the transmission ratio of the step-up gear unit within the transmission ratio ranges can in each case be continuously varied by means of a hydrostatic variator in the area of the hydrostatic branch. Furthermore, in the area of an auxiliary drive output shaft configured as a countershaft, the step-up gear unit is coupled on the transmission input side to the drive engine. The auxiliary drive output shaft is connected by way of gearwheel pairs to a central transmission shaft and to hydraulic pumps and to a hydrostatic shaft also configured as a countershaft.
Owing to the high power to be provided in each case during operation by the auxiliary drive output shaft to various devices, besides the central transmission shaft by way of which the power flow for driving operation is transmitted the auxiliary drive output shaft too has to be made with correspondingly large dimensions, so that the weight of the step-up gear unit is large and its production costs are undesirably high.